Investors are seeking greater transparency from Nike related to its political spending and putting a proposal demanding regular reporting on political contributions to a vote on Thursday.

The vote, at the company’s annual general meeting in Beaverton, Ore., comes a few weeks after the sportswear giant unveiled an advertising campaign featuring NFL quarterback-turned-activist Colin Kaepernick. The campaign led some consumers to call for a boycott of the company and others to buy more of its sneakers.

Political spending refers to money going to lobbying firms, to trade associations’ lobbying efforts, to nonprofits involved in legislation design, as well as direct donations to political campaigns. Investors pushing for greater disclosures want to ensure a company’s core values are aligned with its contributions.

Nike’s board is recommending that its shareholders vote against the resolution for greater political-spending transparency, adding that the company’s existing policies and disclosures have proper oversight and give shareholders enough information to evaluate any risk related to political contributions, according to its proxy statement.

Enhanced transparency as advocated by the proposal would put Nike at a “competitive disadvantage,” according to the proxy statement, because it would reveal “strategies and priorities designed to protect the economic future” of the company.

Nike didn’t respond to a request for comment.

“Nike has the most convoluted and opaque policies of all the companies we’ve examined and negotiated with over more than a decade now,” said Bruce Herbert, founder of Seattle-based Newground Social Investment, a responsible investing fund with around $100 million in assets, and Investor Voice, an investor advocacy group. Investor Voice is the main proponent of the resolution.

Investors concerned with social issues have turned the heat on companies, seeking greater political spending disclosure. Shareholder resolutions advancing this issue made up 11% of all resolutions related to governance, the environment and social issues in 2018, according to a review by law firm Gibson, Dunn & Crutcher LLP.

A slew of large companies have in recent years adopted greater disclosures in light of the risks to their reputation and business, although none of them have ever received majority voting against board opposition, according to the Center for Political Accountability, a Washington, D.C. nonprofit that monitors corporations’ policies and practices regarding political spending.

A mismatch between a company’s core values and political contributions can tarnish a company’s reputation and business, but Nike has resisted repeated demands for greater disclosure, some investors said. The company has received proposals for improved political spending disclosures five times since 2012, and last year it garnered 30% support from shareholders.

“Companies cannot count on their political spending remaining secret [these days],” Bruce Freed, the president of the Center for Political Accountability, said in an email. “There’s the risk of inadvertent disclosure. If the spending is seen as conflicting with company values and positions, companies risk a sharp public backlash.”

The organization has been tracking S&P 500 companies since 2015. There has been a steady increase in the quantity and quality of disclosures and oversight of spending in recent years, Mr. Freed said.

The Center publishes an annual index ranking companies by their political spending disclosure and practices. The index, created in partnership with the Zicklin Center for Business Ethics Research at The Wharton School at the University of Pennsylvania, will be released Oct. 2, and will show the number of companies with high scores for transparency and accountability will double from last year’s report, Mr. Freed said.